Epitaxial growth of p-type cladding regions using nitrogen gas for a gallium and nitrogen containing laser diode

ABSTRACT

In an example, the present invention provides a method for fabricating a light emitting device configured as a Group III-nitride based laser device. The method also includes forming a gallium containing epitaxial material overlying the surface region of a substrate member. The method includes forming a p-type (Al,In,Ga)N waveguiding material overlying the gallium containing epitaxial material under a predetermined process condition. The method includes maintaining the predetermined process condition such that an environment surrounding a growth of the p-type (Al,In,Ga)N waveguide material is substantially a molecular N 2  rich gas environment. The method includes maintaining a temperature ranging from 725 C to 925 C during the formation of the p-type (Al,In,Ga)N waveguide material, although there may be variations. In an example, the predetermined process condition is substantially free from molecular H 2  gas.

BACKGROUND

In 1960, the laser was first demonstrated by Theodore H. Maiman atHughes Research Laboratories in Malibu. This laser utilized asolid-state flash lamp-pumped synthetic ruby crystal to produce redlaser light at 694 nm. By 1964, blue and green laser output wasdemonstrated by William Bridges at Hughes Aircraft utilizing a gas laserdesign called an Argon ion laser. The Ar-ion laser utilized a noble gasas the active medium and produce laser light output in the UV, blue, andgreen wavelengths including 351 nm, 454.6 nm, 457.9 nm, 465.8 nm, 476.5nm, 488.0 nm, 496.5 nm, 501.7 nm, 514.5 nm, and 528.7 nm. The Ar-ionlaser had the benefit of producing highly directional and focusablelight with a narrow spectral output, but the wall plug efficiency was<0.1%, and the size, weight, and cost of the lasers were undesirable aswell.

As laser technology evolved, more efficient lamp pumped solid statelaser designs were developed for the red and infrared wavelengths, butthese technologies remained a challenge for blue and green and bluelasers. As a result, lamp pumped solid state lasers were developed inthe infrared, and the output wavelength was converted to the visibleusing specialty crystals with nonlinear optical properties. A green lamppumped solid state laser had 3 stages: electricity powers lamp, lampexcites gain crystal which lasers at 1064 nm, 1064 nm goes intofrequency conversion crystal which converts to visible 532 nm. Theresulting green and blue lasers were called “lamped pumped solid statelasers with second harmonic generation” (LPSS with SHG) had wall plugefficiency of ˜1%, and were more efficient than Ar-ion gas lasers, butwere still too inefficient, large, expensive, fragile for broaddeployment outside of specialty scientific and medical applications.Additionally, the gain crystal used in the solid state lasers typicallyhad energy storage properties which made the lasers difficult tomodulate at high speeds which limited its broader deployment.

To improve the efficiency of these visible lasers, high power diode (orsemiconductor) lasers were utilized. These “diode pumped solid statelasers with SHG” (DPSS with SHG) had 3 stages: electricity powers 808 nmdiode laser, 808 nm excites gain crystal, which lasers at 1064 nm, 1064nm goes into frequency conversion crystal which converts to visible 532nm. The DPSS laser technology extended the life and improved the wallplug efficiency of the LPSS lasers to 5-10%, and furthercommercialization ensue into more high-end specialty industrial,medical, and scientific applications. However, the change to diodepumping increased the system cost and required precise temperaturecontrols, leaving the laser with substantial size, power consumptionwhile not addressing the energy storage properties which made the lasersdifficult to modulate at high speeds.

As high power laser diodes evolved and new specialty SHG crystals weredeveloped, it became possible to directly convert the output of theinfrared diode laser to produce blue and green laser light output. These“directly doubled diode lasers” or SHG diode lasers had 2 stages:electricity powers 1064 nm semiconductor laser, 1064 nm goes intofrequency conversion crystal which converts to visible 532 nm greenlight. These lasers designs are meant to improve the efficiency, costand size compared to DPSS-SHG lasers, but the specialty diodes andcrystals required make this challenging today. Additionally, while thediode-SHG lasers have the benefit of being directly modulate-able, theysuffer from severe sensitivity to temperature which limits theirapplication. Currently the only viable direct violet, blue, and greenlaser diode structures are fabricated from the wurtzite AlGaInN materialsystem. However, limitations associated with III-nitride laser deviceepitaxial growth and fabrication are numerous and only become moresevere with increased lasing wavelength. These and other limitations aredescribed throughout the present specification and more particularlybelow.

From the above, improved techniques for manufacturing semiconductorlaser diodes are highly desired.

SUMMARY

The invention is directed techniques, including a method of fabricationof optoelectronic devices from semiconductor wafers. In particular, theinvention provides a method and device for emitting electromagneticradiation using nonpolar or semipolar gallium containing substrates suchas GaN, AN, InN, InGaN, AlGaN, AlInGaN, and others. In other examples,novel structures are also included. The invention provides a method anddevice using a gallium and nitrogen containing substrate of the wurtzitecrystal structure configured on any of the (0001), {11-20}, {10-10},{10-11}, {20-21} and {30-31} families of crystal planes or an offcut ofany of these planes according to one or more embodiments, but there canbe other configurations. For example, it is possible under certaincircumstances to produce gallium and nitrogen containing substrates withzinc blende crystal structures which would be applicable under thisinvention. Still more particularly, this invention provides a method forprocessing small semiconductor wafers or non-standard size such that allmultiple wafers can be processed in parallel at the majority of steps inthe fabrication process. The invention can be applied to optical devicessuch as lasers and light emitting diodes, among other devices.

This current invention provides a method for producing low resistance,low optical loss epitaxially grown p-type (Al,In,Ga)N cladding materialwith low Mg-doping levels at low growth temperatures. Herein the p-type(Al,In,Ga)N cladding material is epitaxially grown on top of n-type(Al,In,Ga)N layers under N₂ ambient conditions or ambient conditionsconsisting of a mixture of H₂ and N₂ gases. Under conventional art, itis believed that H₂ (i.e., hydrogen gas) ambient conditions are oftenrequired for growth of high quality low-resistance p-type (Al,In,Ga)Ncladding. Based on first principle calculations by Neugebauer et al.(Neugebauer APL 68, 1829 (1996)), growth of p-type GaN under H₂ richconditions lowers defect concentration while increases acceptor dopantincorporation. Our method for producing p-type (Al,In,Ga)N claddinglayers shows that H₂ ambient conditions are not necessary for achievinghigh quality p-type (Al,In,Ga)N material. In fact, under identicalgrowth rates, p-type cladding material grown under N₂ ambient conditionsare shown to have higher charge and lower sheet resistance compared top-type (Al,In,Ga)N cladding material grown under H₂ ambient conditionswhen grown at sufficiently low temperatures. Low temperature p-type(Al,In,Ga)N cladding material growth is desirable for long wavelengthemitters to prevent thermal degradation of the high indium compositionactive region. Higher performance p-type cladding material grown underN₂ ambient conditions is attributed to lower [C] impurity levelscompared to p-type (Al,In,Ga)N cladding material grown under H₂ ambientconditions. In a preferred embodiment, the p-type (Al,In,Ga)N claddingmaterial of an optoelectronic device is epitaxially grown under pure N₂ambient conditions at sufficiently low temperatures as not to causethermal degradation in the high InN fraction active region. Inalternative embodiment, the p-type (Al,In,Ga)N cladding material of anoptoelectronic device is epitaxially grown under a mixture of N₂/H₂ambient conditions at sufficiently low temperatures as not to causethermal degradation in the high InN fraction active region. In bothembodiments, the Mg-doping in p-type (Al,In,Ga)N cladding material iskept sufficiently low to maintain low optical absorption by the p-typelayers.

Additional benefits are achieved over pre-existing techniques using theinvention. In particular, the invention enables a cost-effective opticaldevice for laser applications. In a specific embodiment, the presentoptical device can be manufactured in a relatively simple and costeffective manner. Depending upon the embodiment, the present apparatusand method can be manufactured using conventional materials and/ormethods according to one of ordinary skill in the art. The present laserdevice uses a non-polar or semipolar gallium nitride material capable ofachieving a blue or green laser device, among others. In one or moreembodiments, the laser device is capable of emitting long wavelengthssuch as those ranging from about 480 nm to greater than about 540 nm,but can be others such as 540 nm to 660 nm and 420 nm to 480 nm.Depending upon the embodiment, one or more of these benefits may beachieved. Of course, there can be other variations, modifications, andalternatives.

A further understanding of the nature and advantages of the inventionmay be realized by reference to the latter portions of the specificationand attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram illustrating (a) V_(f) measured at 14kA/cm² and (b) slab optical loss for laser devices with differentMg-doping concentrations in the first 300 nm of the H₂ ambient grownp-type cladding layer in an example.

FIG. 2 is a simplified diagram illustrating Mg SIMS stack showing Mgconcentrations for two different Cp₂Mg flow rates (5 and 10 sccm) in anexample (under nominally identical rates, the Mg incorporation ratebetween N₂ ambient and H₂ ambient growth p-type GaN is comparable).

FIG. 3 is a simplified diagram illustrating sheet resistance and carrierconcentration measured for p-type GaN grown under H₂ ambient 950 Ctemperature, H₂ ambient 900 C temperature, N₂ ambient 950 C temperature,and N₂ ambient 900 C temperature conditions in an example.

FIG. 4 is a simplified diagram illustrating [C], [Mg], and [O] levelsmeasured from p-type GaN grown under 900 C temperature H₂ ambient, 950 Ctemperature H₂ ambient, and 900 C temperature N₂ ambient conditions inan example.

FIG. 5 is a simplified diagram illustrating V_(f) measured at 14 kA/cm²and slab optical loss values for laser devices with different Mg-dopingprofiles in the p-type cladding layers grown under H₂ and N₂ ambientconditions in an example (the relative Mg concentration increases fromleft to right).

FIG. 6 is a simplified diagram of a flow chart illustrating primarysteps in fabricating a nitride semiconductor device and the method offorming an epitaxial wafer according to an example.

FIG. 7 is an illustration of a simplified schematic cross-sectionaldiagram illustrating a state of the art laser diode structure in anexample.

FIG. 8 is an illustration of a perspective view diagram of a laser diodeaccording to an example.

DETAILED DESCRIPTION OF THE INVENTION

This invention presents a method fabricating a III-nitride optical P-Njunction device e.g., laser, LED. What follows is a general descriptionof the typical configuration and fabrication of these devices.

As we discovered, extending emission wavelength from the violet into thegreen spectra region often requires increasing InN fraction in theactive region. Due to the large lattice mismatch between GaN and InN,high InN fractions in the active region typically results in lowchemical stability of the active layers. Thermal degradation via thermalannealing during the subsequent p-type (Al,In,Ga)N layer growth has beenreported by various groups. Moreover, this phenomenon has beenuniversally observed regardless of growth orientation. It is thereforedesirable to maintain a low post-active region growth thermal budget.

In addition to growth challenges associated with long wavelength laserdevices are waveguide design issues. Refractive index dispersion leadsto a decrease in refractive index contrast between optical waveguidelayers with increasing wavelength. For the same waveguide material, themodal confinement in the active region decreases with increasingemission wavelength. This has a concomitant effect on optical loss,since overlap with passive regions will increase as well. In particular,increased loss from activated Mg acceptors can severely degrade laserdiode performance. It is therefore desirable to have p-type claddinglayers with low Mg concentrations while maintaining acceptable diodevoltages.

Growth of high quality p-type cladding material with low resistance andlow optical loss, however, is particularly difficult under theconstraints of post-active region thermal budget. Lower temperatureand/or high growth rate p-type cladding growth typically results inhigher [C] impurity concentrations. Since [C] is often regarded as adeep level trap, Mg-doping in these layers must be kept relatively highin order to achieve acceptable diode resistance. In laser diodes, thiscomes at the expense of optical loss.

In an example, devices include a gallium and nitrogen containingsubstrate (e.g., GaN) comprising a surface region oriented in either asemipolar or non-polar configuration, but can be others. The device alsohas a gallium and nitrogen containing material comprising InGaNoverlying the surface region. In a specific embodiment, the presentlaser device can be employed in either a semipolar or non-polar galliumcontaining substrate, as described below. As used herein, the term“substrate” can mean the bulk substrate or can include overlying growthstructures such as a gallium and nitrogen containing epitaxial region,or functional regions such as n-type GaN, combinations, and the like. Wehave also explored epitaxial growth and cleave properties on semipolarcrystal planes oriented between the nonpolar m-plane and the polarc-plane. In particular, we have grown on the {30-31} and {20-21}families of crystal planes. We have achieved promising epitaxystructures and cleaves that will create a path to efficient laser diodesoperating at wavelengths from about 400 nm to green, e.g., 500 nm to 540nm. These results include bright blue epitaxy in the 450 nm range,bright green epitaxy in the 520 nm range, and smooth cleave planesorthogonal to the projection of the c-direction. It is desirable toalign the laser cavities parallel to the projection of the c-directionfor maximum gain on this family of crystal planes.

In a specific embodiment, the gallium nitride substrate member is a bulkGaN substrate characterized by having a semipolar or non-polarcrystalline surface region, but can be others. In a specific embodiment,the bulk nitride GaN substrate comprises nitrogen and has a surfacedislocation density between about 10E5 cm⁻² and about 10E7 cm⁻² or below10E5 cm⁻². The nitride crystal or wafer may compriseAl_(x)In_(y)Ga_(1-x-y)N, where 0≦x, y, x+y≦1. In one specificembodiment, the nitride crystal comprises GaN. In one or moreembodiments, the GaN substrate has threading dislocations, at aconcentration between about 10E5 cm⁻² and about 10E8 cm⁻², in adirection that is substantially orthogonal or oblique with respect tothe surface. As a consequence of the orthogonal or oblique orientationof the dislocations, the surface dislocation density is between about10E5 cm⁻² and about 10E7 cm⁻² or below about 10E5 cm⁻². In a specificembodiment, the device can be fabricated on a slightly off-cut semipolarsubstrate as described in U.S. Ser. No. 12/749,466 filed Mar. 29, 2010,which claims priority to U.S. Provisional No. 61/164,409 filed Mar. 28,2009, both of which are commonly assigned and hereby incorporated byreference herein.

The substrate typically is provided with one or more of the followingepitaxially grown elements, but is not limiting:

-   -   an n-GaN cladding region with a thickness of 50 nm to about 6000        nm with a Si or oxygen doping level of about 5E16 cm⁻³ to 1E19        cm⁻³    -   an InGaN region of a high indium content and/or thick InGaN        layer(s) or Super SCH region;    -   a higher bandgap strain control region overlying the InGaN        region;    -   optionally, an SCH region overlying the InGaN region;    -   multiple quantum well active region layers comprised of three to        five or four to six 3.0-5.5.0 nm InGaN quantum wells separated        by 1.5-10.0 nm GaN barriers    -   optionally, a p-side SCH layer comprised of InGaN with molar a        fraction of indium of between 1% and 10% and a thickness from 15        nm to 100 nm    -   an electron blocking layer comprised of AlGaN with molar        fraction of aluminum of between 5% and 20% and thickness from 10        nm to 15 nm and doped with Mg.    -   a p-GaN cladding layer with a thickness from 400 nm to 1000 nm        with Mg doping level of 5E17 cm⁻³ to 1E19 c m⁻³    -   a p++-GaN contact layer with a thickness from 20 nm to 40 nm        with Mg doping level of 1E20 cm⁻³ to 1E21 cm⁻³

Typically each of these regions is formed using at least an epitaxialdeposition technique of metal organic chemical vapor deposition (MOCVD),molecular beam epitaxy (MBE), or other epitaxial growth techniquessuitable for GaN growth. The active region can include one to twentyquantum well regions according to one or more embodiments. As an examplefollowing deposition of the n-type Al_(u)In_(v)Ga_(1-u-v)N layer for apredetermined period of time, so as to achieve a predeterminedthickness, an active layer is deposited. The active layer may comprise asingle quantum well or a multiple quantum well, with 2-10 quantum wells.The quantum wells may comprise InGaN wells and GaN barrier layers. Inother embodiments, the well layers and barrier layers compriseAl_(w)In_(x)Ga_(1-w-x)N and Al_(y)In_(z)Ga_(1-y-z)N, respectively, where0≦w, x, y, z, w+x, y+z≦1, where w<u, y and/or x>v, z so that the bandgapof the well layer(s) is less than that of the barrier layer(s) and then-type layer. The well layers and barrier layers may each have athickness between about 1 nm and about 15 nm. In another embodiment, theactive layer comprises a double heterostructure, with an InGaN orAlwInxGa1−w−xN layer about 10 nm to 100 nm thick surrounded by GaN orAl_(y)In_(z)Ga_(1-y-z)N layers, where w<u, y and/or x>v, z. Thecomposition and structure of the active layer are chosen to providelight emission at a preselected wavelength. The active layer may be leftundoped (or unintentionally doped) or may be doped n-type or p-type.

The active region can also include an electron blocking region, and aseparate confinement heterostructure. In some embodiments, an electronblocking layer is preferably deposited. The electron-blocking layer maycomprise Al_(s)In_(t)Ga_(1-s-t)N, where 0≦s, t, s+t≦1, with a higherbandgap than the active layer, and may be doped p-type or the electronblocking layer comprises an AlGaN/GaN super-lattice structure,comprising alternating layers of AlGaN and GaN. Alternatively, there maybe no electron blocking layer. As noted, the p-type gallium nitridestructure, is deposited above the electron blocking layer and activelayer(s). The p-type layer may be doped with Mg, to a level betweenabout 10E16 cm-3 and 10E22 cm-3, and may have a thickness between about5 nm and about 1000 nm. The outermost 1-50 nm of the p-type layer may bedoped more heavily than the rest of the layer, so as to enable animproved electrical contact. These and other features of the presentinvention can be found throughout the present specification and moreparticularly below.

In an example, the present invention provides a method for fabricating alight emitting device configured as a Group III-nitride based laserdevice. The method includes providing a substrate member comprising agallium and nitrogen containing material and a surface region. Themethod also includes forming a gallium containing epitaxial materialoverlying the surface region. The method includes forming a p-type(Al,In,Ga)N waveguiding material overlying the gallium containingepitaxial material under a predetermined process condition. The methodincludes maintaining the predetermined process condition such that anenvironment surrounding a growth of the p-type (Al,In,Ga)N waveguidematerial is substantially a molecular N₂ rich gas environment. Themethod includes maintaining a temperature ranging from 725 C to 925 Cduring the formation of the p-type (Al,In,Ga)N waveguide material,although there may be variations. In an example, the predeterminedprocess condition is substantially free from molecular H₂ gas. Ofcourse, there can be other variations, modifications, and alternatives.

In an example, the p-type (Al,In,Ga)N waveguiding material is grownunder the predetermined process consisting of the substantiallymolecular N₂ rich gas environment and the molecular H₂ to N₂ gas flowratio into the reactor is less than 1 to 10; wherein the p-type(Al,In,Ga)N waveguiding material is grown at the temperature rangeduring the predetermined process; wherein the p-type (Al,In,Ga)Nwaveguiding material is characterized by a carbon impurity concentrationof less than 1E17 atoms per cubic centimeter when grown at thetemperature range. In an example, the p-type (Al,In,Ga)N waveguidingmaterial is formed using a trimethylgallium metallorganic precursorand/or a triethylgallium metallorganic precursor with a growth rategreater than 0.75 angstrom per second and less than 5. angstrom persecond; wherein the p-type (Al,In,Ga)N waveguiding material is formed atthe predetermined condition including an ammonia containing species,whereupon the ammonia containing species to molecular N₂ gas ratio isgreater than 1:5 but less than 2:3; and further comprising forming ann-type gallium nitride material below the p-type (Al,In,Ga)N waveguidingmaterial, the p-type (Al,In,Ga)N waveguiding material is configured as acladding region.

In an example, the method also includes forming an active regionoverlying the gallium containing epitaxial material, the active regioncomprising of a plurality of quantum-well regions, each of thequantum-well regions being configured with a barrier material; andfurther comprising forming an active region overlying the galliumcontaining epitaxial material, the active region comprising of aplurality of quantum-well regions, each of the quantum-well regionsbeing configured with a barrier material; and further comprising forminga p-type (Al,In,Ga)N p-type electron blocking layer overlying the activeregion.

The method can also include forming an active region overlying thegallium containing epitaxial material, the active region comprising of aplurality of quantum-well regions, each of the quantum-well regionsbeing configured with a barrier material; and further comprising ann-type waveguiding material underneath the active region in an example.

In an alternative example, the method includes forming an active regionoverlying the gallium containing epitaxial material, the active regioncomprising of a plurality of quantum-well regions, each of thequantum-well regions being configured with a barrier material; andwherein the n-type waveguiding material is comprised of a material withan refractive index lower than the average refractive index of theactive region but larger than the n-type cladding material such asindium gallium nitride with indium nitride alloy composition greaterthan 2% but less than 15%.

In an example, the method includes forming an active region overlyingthe gallium containing epitaxial material, the active region comprisingof a plurality of quantum-well regions, each of the quantum-well regionsbeing configured with a barrier material; and wherein the n-typecladding material is comprised of a material with an refractive indexlower than that of the n-type waveguiding material, the material beingat least one of an aluminum gallium nitride with aluminum nitride alloycompositions greater than 0% but less than 20%.

In an example, the method includes forming an active region overlyingthe gallium containing epitaxial material, the active region comprisingof a plurality of quantum-well regions, each of the quantum-well regionsbeing configured with a barrier material; and further comprising ap-type waveguiding material overlying the active region; and wherein thep-type waveguiding material is comprised of a material with anrefractive index lower than the average refractive index of the activeregion but larger than the p-type cladding material such as indiumgallium nitride with indium nitride alloy composition greater than 2%but less than 15%.

In an example, the method includes forming an active region overlyingthe gallium containing epitaxial material, the active region comprisingof a plurality of quantum-well regions, each of the quantum-well regionsbeing configured with a barrier material; and wherein the p-typecladding material is comprised of a material with an refractive indexlower than that of the p-type waveguiding material such as aluminumgallium nitride with aluminum nitride alloy compositions greater than 0%but less than 20%.

In an example, the method includes forming an active region overlyingthe gallium containing epitaxial material, the active region comprisingof a plurality of quantum-well regions, each of the quantum-well regionsbeing configured with a barrier material; and further comprising anactive region with defect suppression regions.

In an example, the p-type (Al,In,Ga)N waveguiding material has athickness from 400 to 1000 nanometer with Mg doping level of 5E17 to2E19 atoms per cubic centimeter, the waveguiding material beingconfigured as a waveguiding material and a cladding region.

In an example, the method includes forming a highly Mg doped p++ contactlayer with a thickness greater than 5 nanometer but lower than 50nanometer overlying the p-type (Al,In,Ga)N waveguiding material.

In an example, the method further includes introducing a metallorganicor a combination of metallogranic precursors consisting of a groupincluding trimethylgallium, triethylgallium, trimethylaluminum,trimethylindium, or Bis(cyclopentadienyl)magnesium in forming the p-type(Al,In,Ga)N waveguiding material; and wherein the p-type (Al,In,Ga)Nwaveguiding material is grown using MOCVD or MBE.

In an example, the substrate is configured on a nonpolar (10-10),(11-20), or a related miscut orientation. In an example, the substrateis configured on polar (0001) or (000-1), or a related miscutorientation. In an example, the substrate is configured on a semipolar(20-21), (20-2-1), (30-31), (30-3-1), (11-22), or a related miscutorientation.

In an example, the method can include a misfit dislocation blockingfeature configured to the substrate. In an example, the method includesforming a conductive oxide material comprising either an indium tinoxide material or a zinc oxide material overlying the p-type (Al,In,Ga)Nmaterial waveguiding material; and forming a metallization layerselected from at least one of Au, Ni, Pd, Al, Pt, or Ti overlying theconductive oxide layer. In an example, the diode voltage of the deviceis less than 6.75 V at a current density of 14 kA/cm2. In an example,the area on wafer affected by dark spot defects is less than 10%. In anexample, the slab optical loss of the device is less than 10 cm-1.

In an example, the invention provides a method for fabricating a lightemitting device configured as a Group III-nitride based laser device. Inan example, the method includes providing a substrate member comprisinga gallium and nitrogen containing material and a surface region andforming a gallium containing epitaxial material overlying the surfaceregion. In an example, the method includes forming a p-type (Al,In,Ga)Nwaveguiding material overlying the gallium containing epitaxial materialunder a predetermined process condition. The method includes maintainingthe predetermined process condition such that an environment surroundinga growth of the p-type (Al,In,Ga)N waveguide material is substantially amolecular N₂ rich gas environment. In an example, the method includesmaintaining a temperature ranging from 725 C to 925 C during theformation of the p-type (Al,In,Ga)N waveguide material. In an example,the predetermined process condition is substantially free from molecularH₂ gas. In an example, the predetermined process condition comprisinginitiating formation under the substantially molecular N₂ rich gasambient condition for a first thickness of material and forming a secondthickness of material under a non-substantially molecular N₂ rich gasenvironment.

In an alternative example, the invention provides a method forfabricating a light emitting device configured as a Group III-nitridebased laser device. In an example, the method includes providing asubstrate member comprising a gallium and nitrogen containing materialand a surface region. In an example, the method includes forming agallium containing epitaxial material overlying the surface region andforming a p-type (Al,In,Ga)N waveguiding material overlying the galliumcontaining epitaxial material under a predetermined process condition,the predetermined process condition being substantially free frommolecular H₂ gas. In an example, the method includes maintaining thepredetermined process condition such that an environment surrounding agrowth of the p-type (Al,In,Ga)N waveguide material is substantially amolecular N₂ rich gas environment, while maintaining a temperatureranging from 725 C to 925 C during the formation of the p-type(Al,In,Ga)N waveguide material; and further comprising forming an n-typegallium nitride material below the p-type (Al,In,Ga)N waveguidingmaterial, the p-type (Al,In,Ga)N waveguiding material is configured as acladding region. In an example, the method includes forming an activeregion overlying the gallium containing epitaxial material, the activeregion comprising of a plurality of quantum-well regions, each of thequantum-well regions being configured with a barrier material andforming an active region overlying the gallium containing epitaxialmaterial, the active region comprising of a plurality of quantum-wellregions, each of the quantum-well regions being configured with abarrier material; and further comprising forming a p-type (Al,In,Ga)Np-type electron blocking layer overlying the active region. In anexample, the p-type (Al,In,Ga)N waveguiding material is grown under thepredetermined process consisting of the substantially molecular N₂ richgas environment and the molecular H₂ to N₂ gas flow ratio into thereactor is less than 1 to 10; wherein the p-type (Al,In,Ga)N waveguidingmaterial is grown at the temperature range during the predeterminedprocess; wherein the p-type (Al,In,Ga)N waveguiding material ischaracterized by a carbon impurity concentration of less than 1E17 atomsper cubic centimeter when grown at the temperature range. In an example,the p-type (Al,In,Ga)N waveguiding material is formed using atrimethylgallium metallorganic precursor and/or a triethylgalliummetallorganic precursor with a growth rate greater than 0.75 angstromper second and less than 5.0 angstrom per second. In an example, thep-type (Al,In,Ga)N waveguiding material is formed at the predeterminedcondition including an ammonia containing species, whereupon the ammoniacontaining species to molecular N₂ gas ratio is greater than 1:5 butless than 2:3. In an example, the substrate is configured on a nonpolar(10-10), (11-20), or a related miscut orientation or wherein thesubstrate is configured on polar (0001) or (000-1), or a related miscutorientation or wherein the substrate is configured on a semipolar(20-21), (20-2-1), (30-31), (30-3-1), (11-22), or a related miscutorientation. Further details of the present techniques can be foundthroughout the present specification and more particularly below.

FIG. 1 shows (a) V_(f) measured at 14 kA/cm² and (b) slab optical lossfor laser devices with different Mg-doping concentrations in the first300 nm of the H₂ ambient grown p-type cladding layer. Slab optical lossincreases as device voltage is reduced via increased Mg-doping.

This inventions provides a method for fabricating high quality p-type(Al,In,Ga)N at low temperatures. By growing p-type (Al,In,Ga)N layersunder N₂ ambient conditions, lower sheet resistance and higher carrierconcentrations can be achieved.

FIG. 2 is a simplified diagram illustrating Mg SIMS stack showing Mgconcentrations for two different Cp₂Mg flow rates (5 and 10 sccm) in anexample. As shown, under nominally identical rates, the Mg incorporationrate between N₂ ambient and H₂ ambient growth p-type GaN is comparable.

FIG. 3 shows Sheet resistance and carrier concentration measured forp-type GaN grown under H₂ ambient 950 C temperature, H₂ ambient 900 Ctemperature, N₂ ambient 950 C temperature, and N₂ ambient 900 Ctemperature conditions. 900 C temperature H₂ ambient grown p-type(Al,In,Ga)N is characterized by high sheet resistance and low carrierconcentrations. By increasing the growth temperature, higher qualityp-type (Al,In,Ga)N can be achieved. However, comparable performancep-type (Al,In,Ga)N material can also be achieved by growing under lowtemperature N₂ ambient conditions. Increasing growth temperature underN₂ ambient conditions does not further improve p-type (Al,In,Ga)Nquality.

FIG. 4 compares carbon, magnesium, and oxygen levels measured fromp-type GaN grown under 900 C temperature H₂ ambient, 950 C temperatureH₂ ambient, and 900 C temperature N₂ ambient conditions. All threeconditions exhibit comparable Mg and O levels when grown under nominallyidentical growth rates. Carbon levels, however, are significantly higherfor low temperature H₂ ambient p-type GaN, while low temperature N₂ambient p-type GaN and high temperature H₂ ambient p-type GaN exhibitcomparable carbon levels.

Lower carbon levels for low temperature N₂ ambient p-type layers enablesgrowth of high quality p-type (Al,In,Ga)N cladding layers with lower Mgdoping concentrations. FIG. 5 shows V_(f) measured at 14 kA/cm2 and slaboptical loss values for laser devices with different Mg-doping profilesin the p-type cladding layers grown under H₂ and N₂ ambient conditions.The relative Mg concentration increases from left to right. Optical lossdecreases with decreasing Mg concentrations. Mg concentrations in p-typecladding layers grown under H₂ ambient conditions can only be lowered tointermediate Mg concentrations before Vf becomes unacceptably high. Mgconcentrations in p-type cladding layers grown under N₂ ambientconditions, however, can be lowered much further before Vf increase isobserved.

This invention resolves two main epitaxial growth issues regarding longwavelength laser devices:

-   -   1. Degradation of high InN content active regions due to thermal        annealing during growth of post-active region p-type (Al,In,Ga)N        waveguiding and cladding layers.    -   2. High optical loss due to modal overlap with passive p-type        (Al,In,Ga)N waveguiding and cladding layers.

FIG. 6 is a simplified diagram of a flow chart illustrating primarysteps in fabricating a nitride semiconductor device and the method offorming an epitaxial wafer according to an example. This diagram ismerely an example, which should not unduly limit the scope of the claimsherein. One of ordinary skill in the art would recognize manyalternatives, variations, and modifications in light of the presentdisclosure. In this example, the substrate wafer is placed into thereactor and brought up to temperatures 1175 C>T>700 C under either H₂ orN₂ rich ambient conditions. N-type cladding and/or waveguiding(Al,In,Ga)N material is grown under H₂ or N₂ rich ambient conditions.Light emitting active material, typically consisting a plurality ofInGaN quantum-wells and (Al,In,Ga)N quantum-barriers, is grown on top ofthe n-type cladding/waveguiding material. In some practices, an p-type(Al,In,Ga)N material (electron blocking layer) with bandgap larger thanthat of the quantum-well and quantum-barrier is grown on top of thelight emitting active material. P-type cladding and/or waveguiding(Al,In,Ga)N material is then subsequently grown. In this specificexample, the p-type cladding and/or waveguiding (Al,In,Ga)N material isgrown under N₂ rich conditions with growth temperatures in the ranges of700 C>T>950 C. The method of our invention is most useful within thistemperature range. After the p-type cladding/waveguiding (Al,In,Ga)Nmaterial growth, the epitaxial structure is capped with a Mg doped(Al,In,Ga)N p-contact layer with thickness in the range of 5 to 45 nm.After the p-contact layer is grown, the temperature in the reactor isramped down to room temperature and the substrate is unloaded from thereactor. Laser device patterns, including electrode metallization, arethen made on the wafers using standard microelectronic fabricationprocesses.

In a preferred embodiment, the p-type (Al,In,Ga)N cladding material ofan optoelectronic device is epitaxially grown under pure N₂ ambientconditions at sufficiently low temperatures as not to cause thermaldegradation in the high InN fraction active region. In a secondembodiment, the p-type (Al,In,Ga)N cladding material of anoptoelectronic device is epitaxially grown under a mixture of N₂/H₂ambient conditions at sufficiently low temperatures as not to causethermal degradation in the high InN fraction active region. In a thirdembodiment, portions of the p-type (Al,In,Ga)N cladding material can begrown under a mixture of N₂/H₂ ambient conditions or full N₂ ambientconditions. For example, part of the p-type (Al,In,Ga)N claddingmaterial can be grown under low temperature conditions under N₂ ambientconditions to keep [C] impurity levels low, while other portions of thep-type (Al,In,Ga)N cladding material are grown under high temperatureconditions where [C] impurity levels are not an issue. In thisembodiment, the overall thermal budget is kept low so as not to inducedefect formation in the quantum-well active region. In all embodiments,the Mg-doping in p-type (Al,In,Ga)N cladding material is keptsufficiently low to maintain low optical absorption by the p-typelayers.

Low temperature p-type (Al,In,Ga)N cladding layers grown under N₂ambient conditions can be combined with other technologies to producehigh performance lasers. In an embodiment, a laser device with N₂ambient grown p-type (Al,In,Ga)N cladding material can be grown onsemipolar orientation substrates that have been patterned withdislocation blocking features. These features can be patternedlithographically and then dry etched, or can be laser scribed into thewafers. In another embodiment, laser device with defect suppressionlayers in the active region can be combined with p-type (Al,In,Ga)Ncladding material grown under N₂ ambient conditions to produce highquality, low defect epi-structures.

FIG. 7 is a simplified schematic cross-sectional diagram illustrating alaser diode structure according to embodiments of the presentdisclosure. This diagram is merely an example, which should not undulylimit the scope of the claims herein. One of ordinary skill in the artwould recognize other variations, modifications, and alternatives inlight of the present disclosure. As shown, the laser device includesgallium nitride substrate 703, which has an underlying n-type metal backcontact region 701. In an embodiment, the metal back contact region ismade of a suitable material such as those noted below and others. In anembodiment, the device also has an overlying n-type gallium nitridelayer 705, an active region 707, and an overlying p-type gallium nitridelayer structured as a laser stripe region 711 (or p-type waveguidingmaterial). Herein the p-type gallium nitride 711 is grown under N₂ richambient conditions and at sufficiently low temperature as not tothermally degrade the high indium composition active region.Additionally, the device also includes an n-side separate confinementhetereostructure (SCH) 706, p-side guiding layer or SCH 708, p-AlGaN EBL709, among other features. In an embodiment, the device also has a p++type gallium nitride material 713 to form a contact region. Furtherdetails of the contact region can be found throughout the presentspecification and more particularly below.

In an embodiment, the device also has an overlying n-type galliumnitride layer 705, an active region 707, and an overlying p-type galliumnitride layer structured as a laser stripe region 711. Additionally, thedevice also includes an n-side separate confinement hetereostructure(SCH) 706, p-side guiding layer or SCH 708, p-AlGaN EBL 709, among otherfeatures. In an embodiment, the device also has a p++ type galliumnitride material 713 to form a contact region. In an embodiment, the p++type contact region has a suitable thickness and may range from about 10nm to 50 nm, or other thicknesses. In an embodiment, the doping levelcan be higher than the p-type cladding region and/or bulk region. In anembodiment, the p++ type region has doping concentration ranging fromabout 10¹⁹ to 10²¹ Mg/cm³, and others. The p++ type region preferablycauses tunneling between the semiconductor region and overlying metalcontact region. In an embodiment, each of these regions is formed usingat least an epitaxial deposition technique of metal organic chemicalvapor deposition (MOCVD), molecular beam epitaxy (MBE), or otherepitaxial growth techniques suitable for GaN growth. In an embodiment,the epitaxial layer is a high quality epitaxial layer overlying then-type gallium nitride layer. In some embodiments the high quality layeris doped, for example, with Si or O to form n-type material, with adopant concentration between about 10¹⁶ cm⁻³ and 10²⁰ cm⁻³.

The device has a laser stripe region formed overlying a portion of theoff-cut crystalline orientation surface region. As example, FIG. 8 is asimplified schematic diagram of semipolar laser diode with the cavityaligned in the projection of c-direction with cleaved or etched mirrors.The laser stripe region is characterized by a cavity orientationsubstantially in a projection of a c-direction, which is substantiallynormal to an a-direction. The laser strip region has a first end 107 anda second end 109 and is formed on a projection of a c-direction on a{20-21} gallium and nitrogen containing substrate having a pair ofcleaved mirror structures, which face each other. The first cleavedfacet comprises a reflective coating and the second cleaved facetcomprises no coating, an antireflective coating, or exposes gallium andnitrogen containing material. The first cleaved facet is substantiallyparallel with the second cleaved facet. The first and second cleavedfacets are provided by a scribing and breaking process according to anembodiment or alternatively by etching techniques using etchingtechnologies such as reactive ion etching (RIE), inductively coupledplasma etching (ICP), or chemical assisted ion beam etching (CAIBE), orother method. The first and second mirror surfaces each comprise areflective coating. The coating is selected from silicon dioxide,hafnia, and titania, tantalum pentoxide, zirconia, includingcombinations, and the like. Depending upon the design, the mirrorsurfaces can also comprise an anti-reflective coating.

In a specific embodiment, the method of facet formation includessubjecting the substrates to a laser for pattern formation. In apreferred embodiment, the pattern is configured for the formation of apair of facets for one or more ridge lasers. In a preferred embodiment,the pair of facets face each other and are in parallel alignment witheach other. In a preferred embodiment, the method uses a UV (355 nm)laser to scribe the laser bars. In a specific embodiment, the laser isconfigured on a system, which allows for accurate scribe linesconfigured in one or more different patterns and profiles. In one ormore embodiments, the laser scribing can be performed on the back-side,front-side, or both depending upon the application. Of course, there canbe other variations, modifications, and alternatives.

In a specific embodiment, the method uses backside laser scribing or thelike. With backside laser scribing, the method preferably forms acontinuous line laser scribe that is perpendicular to the laser bars onthe backside of the GaN substrate. In a specific embodiment, the laserscribe is generally 15-20 um deep or other suitable depth. Preferably,backside scribing can be advantageous. That is, the laser scribe processdoes not depend on the pitch of the laser bars or other like pattern.Accordingly, backside laser scribing can lead to a higher density oflaser bars on each substrate according to a preferred embodiment. In aspecific embodiment, backside laser scribing, however, may lead toresidue from the tape on one or more of the facets. In a specificembodiment, backside laser scribe often requires that the substratesface down on the tape. With front-side laser scribing, the backside ofthe substrate is in contact with the tape. Of course, there can be othervariations, modifications, and alternatives.

Laser scribe Pattern: The pitch of the laser mask is about 200 um, butcan be others. The method uses a 170 um scribe with a 30 um dash for the200 um pitch. In a preferred embodiment, the scribe length is maximizedor increased while maintaining the heat affected zone of the laser awayfrom the laser ridge, which is sensitive to heat.

Laser scribe Profile: A saw tooth profile generally produces minimalfacet roughness. It is believed that the saw tooth profile shape createsa very high stress concentration in the material, which causes thecleave to propagate much easier and/or more efficiently.

In a specific embodiment, the method of facet formation includessubjecting the substrates to mechanical scribing for pattern formation.In a preferred embodiment, the pattern is configured for the formationof a pair of facets for one or more ridge lasers. In a preferredembodiment, the pair of facets face each other and are in parallelalignment with each other. In a preferred embodiment, the method uses adiamond tipped scribe to physically scribe the laser bars, though aswould be obvious to anyone learned in the art a scribe tipped with anymaterial harder than GaN would be adequate. In a specific embodiment,the laser is configured on a system, which allows for accurate scribelines configured in one or more different patterns and profiles. In oneor more embodiments, the mechanical scribing can be performed on theback-side, front-side, or both depending upon the application. Ofcourse, there can be other variations, modifications, and alternatives.

In a specific embodiment, the method uses backside scribing or the like.With backside mechanical scribing, the method preferably forms acontinuous line scribe that is perpendicular to the laser bars on thebackside of the GaN substrate. In a specific embodiment, the laserscribe is generally 15-20 um deep or other suitable depth. Preferably,backside scribing can be advantageous. That is, the mechanical scribeprocess does not depend on the pitch of the laser bars or other likepattern. Accordingly, backside scribing can lead to a higher density oflaser bars on each substrate according to a preferred embodiment. In aspecific embodiment, backside mechanical scribing, however, may lead toresidue from the tape on one or more of the facets. In a specificembodiment, backside mechanical scribe often requires that thesubstrates face down on the tape. With front-side mechanical scribing,the backside of the substrate is in contact with the tape. Of course,there can be other variations, modifications, and alternatives.

It is well known that etch techniques such as chemical assisted ion beametching (CAIBE), inductively coupled plasma (ICP) etching, or reactiveion etching (RIE) can result in smooth and vertical etched sidewallregions, which could serve as facets in etched facet laser diodes. Inthe etched facet process a masking layer is deposited and patterned onthe surface of the wafer. The etch mask layer could be comprised ofdielectrics such as silicon dioxide (SiO₂), silicon nitride (SixNy), acombination thereof or other dielectric materials. Further, the masklayer could be comprised of metal layers such as Ni or Cr, but could becomprised of metal combination stacks or stacks comprising metal anddielectrics. In another approach, photoresist masks can be used eitheralone or in combination with dielectrics and/or metals. The etch masklayer is patterned using conventional photolithography and etch steps.The alignment lithography could be performed with a contact aligner orstepper aligner. Such lithographically defined mirrors provide a highlevel of control to the design engineer. After patterning of thephotoresist mask on top of the etch mask is complete, the patterns inthen transferred to the etch mask using a wet etch or dry etchtechnique. Finally, the facet pattern is then etched into the waferusing a dry etching technique selected from CAIBE, ICP, RIE and/or othertechniques. The etched facet surfaces must be highly vertical of betweenabout 87 and 93 degrees or between about 89 and 91 degrees from thesurface plane of the wafer. The etched facet surface region must be verysmooth with root mean square roughness values of less than 50 nm, 20 nm,5 nm, or 1 nm. Lastly, the etched must be substantially free fromdamage, which could act as nonradiative recombination centers and hencereduce the COMD threshold. CAIBE is known to provide very smooth and lowdamage sidewalls due to the chemical nature of the etch, while it canprovide highly vertical etches due to the ability to tilt the waferstage to compensate for any inherent angle in etch.

The laser stripe is characterized by a length and width. The lengthranges from about 50 microns to about 3000 microns, but is preferablybetween 10 microns and 400 microns, between about 400 microns and 800microns, or about 800 microns and 1600 microns, but could be others. Thestripe also has a width ranging from about 0.5 microns to about 50microns, but is preferably between 0.8 microns and 2.5 microns forsingle lateral mode operation or between 2.5 um and 50 um formulti-lateral mode operation, but can be other dimensions. In a specificembodiment, the present device has a width ranging from about 0.5microns to about 1.5 microns, a width ranging from about 1.5 microns toabout 3.0 microns, a width ranging from 3.0 microns to about 50 microns,and others. In a specific embodiment, the width is substantiallyconstant in dimension, although there may be slight variations. Thewidth and length are often formed using a masking and etching process,which are commonly used in the art.

The laser stripe is provided by an etching process selected from dryetching or wet etching. The device also has an overlying dielectricregion, which exposes a p-type contact region. Overlying the contactregion is a contact material, which may be metal or a conductive oxideor a combination thereof. The p-type electrical contact may be depositedby thermal evaporation, electron beam evaporation, electroplating,sputtering, or another suitable technique. Overlying the polished regionof the substrate is a second contact material, which may be metal or aconductive oxide or a combination thereof and which comprises the n-typeelectrical contact. The n-type electrical contact may be deposited bythermal evaporation, electron beam evaporation, electroplating,sputtering, or another suitable technique.

P-type (Al,In,Ga)N layers grown epitaxially by MOCVD typically require aH₂ ambient condition. It is universally believed that H₂ ambient growthconditions are necessary to achieve low resistance p-type (Al,In,Ga)N.Our invention shows that at low temperatures, p-type (Al,In,Ga)N grownunder N₂ ambient conditions has lower resistance and higher carrierconcentration than p-type (Al,In,Ga)N grown under H₂ ambient conditions.

Low temperature p-type (Al,In,Ga)N is typically desired in longwavelength emission devices since high InN content active regions areprone to thermal degradation during growth of post-active region layers.High temperature p-type (Al,In,Ga)N growth is problematic for laserdiode devices in particular due to the necessity of a sufficiently thickp-type optical waveguiding material. Long growth times at elevatedtemperature required for thick p-type (Al,In,Ga)N deposition of thecladding leads to degradation of the light emitting layers. The p-type(Al,In,Ga)N cladding material can be grown at low temperatures, but thisusually results in lower quality p-type cladding material due to higherimpurity concentrations that can compensate acceptors. In order to keepdiode voltage low, Mg-doping concentrations must be increased. In laserdiodes, this comes at the expense of optical loss.

As used herein, the term GaN substrate is associated with GroupIII-nitride based materials including GaN, InGaN, AlGaN, or other GroupIII containing alloys or compositions that are used as startingmaterials. Such starting materials include polar GaN substrates (i.e.,substrate where the largest area surface is nominally an (h k l) planewherein h=k=0, and l is non-zero), non-polar GaN substrates (i.e.,substrate material where the largest area surface is oriented at anangle ranging from about 80-100 degrees from the polar orientationdescribed above towards an (h k l) plane wherein l=0, and at least oneof h and k is non-zero) or semipolar GaN substrates (i.e., substratematerial where the largest area surface is oriented at an angle rangingfrom about +0.1 to 80 degrees or 110-179.9 degrees from the polarorientation described above towards an (h k l) plane wherein l=0, and atleast one of h and k is non-zero).

In an example, the present device can be enclosed in a suitable package.Such package can include those such as in TO-38 and TO-56 headers. Othersuitable package designs and methods can also exist, such as TO-9 orflat packs where fiber optic coupling is required and even non-standardpackaging. In a specific embodiment, the present device can beimplemented in a co-packaging configuration such as those described inU.S. Publication No. 2010/0302464, which is incorporated by referenceherein.

In other embodiments, the present laser device can be configured in avariety of applications. Such applications include laser displays,metrology, communications, health care and surgery, informationtechnology, and others. As an example, the present laser device can beprovided in a laser display such as those described in U.S. applicationSer. No. 12/789,303 filed on May 27, 2010, which is incorporated byreference herein.

As used herein, the term “substrate” can mean the bulk substrate or caninclude overlying growth structures such as a gallium and nitrogencontaining epitaxial region, or functional regions such as n-type GaN,combinations, and the like. For semipolar, the present method andstructure includes a stripe oriented perpendicular to the c-axis, anin-plane polarized mode is not an Eigen-mode of the waveguide. Thepolarization rotates to elliptic (if the crystal angle is not exactly 45degrees, in that special case the polarization would rotate but belinear, like in a half-wave plate). The polarization will of course notrotate toward the propagation direction, which has no interaction withthe Al band. The length of the a-axis stripe determines whichpolarization comes out at the next mirror. Although the embodimentsabove have been described in terms of a laser diode, the methods anddevice structures can also be applied to any light emitting diodedevice. Therefore, the above description and illustrations should not betaken as limiting the scope of the present invention which is defined bythe appended claims.

In an example, the present method and system can also include use of oneor more of a variety of wavelength conversion species.

Wavelength conversion materials can be ceramic or semiconductor particlephosphors, ceramic or semiconductor plate phosphors, organic orinorganic downconverters, upconverters (anti-stokes), nano-particles andother materials which provide wavelength conversion. Some examples arelisted below:

(Srn,Ca1−n)10(PO4)6*B2O3:Eu2+ (wherein 0≦n≦1)

(Ba,Sr,Ca)5(PO4)3(Cl,F,Br,OH):Eu2+,Mn2+

(Ba,Sr,Ca)BPO5:Eu2+,Mn2+

Sr2Si3O8*2SrCl2:Eu2+

(Ca,Sr,Ba)3MgSi2O8:Eu2+, Mn2+

BaAl8O13:Eu2+

2SrO*0.84P2O5*0.16B2O3:Eu2+

(Ba,Sr,Ca)MgAl10O17:Eu2+,Mn2+

K2SiF6:Mn4+

(Ba,Sr,Ca)Al2O4:Eu2+

(Y,Gd,Lu,Sc,La)BO3:Ce3+,Tb3+

(Ba,Sr,Ca)2(Mg,Zn)Si2O7:Eu2+

(Mg,Ca,Sr, Ba,Zn)2Si1−xO4−2x:Eu2+(wherein 0≦x≦0.2)

(Ca, Sr, Ba)MgSi2O6: Eu2+

(Sr,Ca,Ba)(Al,Ga)2S4:Eu2+

(Ca,Sr)8(Mg,Zn)(SiO4)4Cl2:Eu2+,Mn2+

Na2Gd2B2O7:Ce3+,Tb3+

(Sr,Ca,Ba,Mg,Zn)2P2O7:Eu2+,Mn2+

(Gd,Y,Lu,La)2O3:Eu3+,Bi3+

(Gd,Y,Lu,La)2O2S:Eu3+,Bi3+

(Gd,Y,Lu,La)VO4:Eu3+,Bi3+

(Ca,Sr)S:Eu2+,Ce3+

(Y,Gd,Tb,La,Sm,Pr,Lu)3(Sc,Al,Ga)5−nO12−3/2n:Ce3+(wherein 0≦n≦0.5)

ZnS:Cu+,Cl−

(Y,Lu,Th)3Al5O12:Ce3+

ZnS:Cu+,Al3+

ZnS:Ag+,Al3+

ZnS:Ag+,Cl−

The group:

-   -   Ca1−xAlx−xySi1−x+xyN2−x−xyCxy:A    -   Ca1−x−zNazM(III)x−xy−zSi1−x+xy+zN2−x−xyCxy:A    -   M(II)1−x−zM(I)zM(III)x−xy−zSi1−x+xy+zN2−x−xyCxy:A    -   M(II)1−x−zM(I)zM(III)x−xy−zSi1−x+xy+zN2−x−xy−2w/3CxyOw−v/2Hv:A    -   M(II)1−x−zM(I)zM(III)x−xy−zSi1−x+xy+zN2−x−xy−2w/3−v/3CxyOwHv:A    -   wherein 0<x<1, 0<y<1, 0≦z<1, 0≦v<1, 0<w<1, x+z<1, x>xy+z, and        0<x−xy−z<1, M(II) is at least one divalent cation, M(I) is at        least one monovalent cation, M(III) is at least one trivalent        cation, H is at least one monovalent anion, and A is a        luminescence activator doped in the crystal structure.    -   LaAl(Si 6−z Al z)(N 10−z Oz):Ce3+(wherein z=1)    -   (Ca, Sr) Ga2S4: Eu2+    -   AlN:Eu2+    -   SrY2S4:Eu2+    -   CaLa2S4:Ce3+    -   (Ba,Sr,Ca)MgP2O7:Eu2+,Mn2+    -   (Y,Lu)2WO6:Eu3+,Mo6+    -   CaWO4    -   (Y,Gd,La)2O2S:Eu3+    -   (Y,Gd,La)2O3:Eu3+    -   (Ba,Sr,Ca)nSinNn:Eu2+(where 2n+4=3n)    -   Ca3(SiO4)Cl2:Eu2+    -   (Y,Lu,Gd)2−nCanSi4N6+nC1−n:Ce3+, (wherein 0≦n≦0.5)    -   (Lu,Ca,Li,Mg,Y) alpha-SiAlON doped with Eu2+ and/or Ce3+    -   (Ca,Sr,Ba)SiO2N2:Eu2+,Ce3+    -   Ba3MgSi2O8:Eu2+,Mn2+    -   (Sr,Ca)AlSiN3:Eu2+    -   CaAlSi(ON)3:Eu2+    -   Ba3MgSi2O8:Eu2+    -   LaSi 3N5:Ce3+    -   Sr10(PO4)6Cl2:Eu2+    -   (BaSi)O12N2:Eu2+    -   M(II)aSibOcNdCe:A wherein (6<a<8, 8<b<14, 13<c<17, 5<d<9, 0<e<2)        and M(II) is a divalent cation of        (Be,Mg,Ca,Sr,Ba,Cu,Co,Ni,Pd,Tm,Cd) and A of        (Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Mn,Bi,Sb)    -   SrSi2(O,Cl)2N2:Eu2+    -   SrSi 9Al19 ON31:Eu2+    -   (Ba,Sr)Si2(O,Cl)2N2:Eu2+    -   LiM2O8:Eu3+ where M=(W or Mo)

For purposes of the application, it is understood that when a phosphorhas two or more dopant ions (i.e. those ions following the colon in theabove phosphors), this is to mean that the phosphor has at least one(but not necessarily all) of those dopant ions within the material. Thatis, as understood by those skilled in the art, this type of notationmeans that the phosphor can include any or all of those specified ionsas dopants in the formulation.

Further, it is to be understood that nanoparticles, quantum dots,semiconductor particles, and other types of materials can be used aswavelength converting materials. The list above is representative andshould not be taken to include all the materials that may be utilizedwithin embodiments described herein.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. Although the technique has been described in terms of a specifictemperature range, there can be variations in some examples. Therefore,the above description and illustrations should not be taken as limitingthe scope of the present invention which is defined by the appendedclaims.

What is claimed is:
 1. A method for fabricating a light emitting deviceconfigured as a Group III-nitride based laser device, the methodcomprising: providing a substrate member comprising a gallium andnitrogen containing material and a surface region; forming a galliumcontaining epitaxial material overlying the surface region; forming ap-type (Al,In,Ga)N waveguiding material overlying the gallium containingepitaxial material under a predetermined process condition; maintainingthe predetermined process condition such that an environment surroundinga growth of the p-type (Al,In,Ga)N waveguiding material is substantiallymolecular N₂ rich gas environment; and maintaining a temperature rangingfrom 725 C to 925 C during the formation of the p-type (Al,In,Ga)Nwaveguiding material; whereupon the predetermined process conditionconsists of the substantially molecular N₂ rich gas environment and amolecular H₂ to N₂ gas flow ratio of less than 1 to 10; wherein thep-type (Al,In,Ga)N waveguiding material is grown at the temperaturerange during the predetermined process condition; wherein the p-type(Al,In,Ga)N waveguiding material is characterized by a carbon impurityconcentration of less than 1E17 atoms per cubic centimeter.
 2. Themethod of claim 1 further comprising forming an active region overlyingthe gallium containing epitaxial material, the active region comprisingof a plurality of quantum-well regions, each of the quantum-well regionsbeing configured with a barrier material; and further comprising forminga p-type (Al,In,Ga)N electron blocking layer overlying the activeregion.
 3. The method of claim 1 further comprising forming an activeregion overlying the gallium containing epitaxial material, the activeregion comprising of a plurality of quantum-well regions, each of thequantum-well regions being configured with a barrier material; andfurther comprising forming an n-type waveguiding material underneath theactive region.
 4. The method of claim 3 wherein the n-type waveguidingmaterial is comprised of a material with a refractive index lower thanan average refractive index of the active region but larger than indiumgallium nitride with indium nitride alloy composition greater than 2%but less than 15%.
 5. The method of claim 4 wherein the n-typewaveguiding material comprises an aluminum gallium nitride with aluminumnitride alloy compositions greater than 0% but less than 20%.
 6. Themethod of claim 1 further comprising forming an active region overlyingthe gallium containing epitaxial material, the active region comprisingof a plurality of quantum-well regions, each of the quantum-well regionsbeing configured with a barrier material; wherein the p-type (Al,In,Ga)Nwaveguiding material overlies the active region; and wherein the p-type(Al,In,Ga)N waveguiding material is comprised of a material with arefractive index lower than an average refractive index of the activeregion but larger than indium gallium nitride with indium nitride alloycomposition greater than 2% but less than 15%.
 7. The method of claim 6wherein the p-type (Al,In,Ga)N waveguiding material comprises aluminumgallium nitride with aluminum nitride alloy compositions greater than 0%but less than 20%.
 8. The method of claim 1 further comprising formingan active region overlying the gallium containing epitaxial material,the active region comprising of a plurality of quantum-well regions,each of the quantum-well regions being configured with a barriermaterial; wherein the active region comprises defect suppressionregions.
 9. The method of claim 1 further comprising forming a highly Mgdoped p++ contact layer with a thickness greater than 5 nanometer butlower than 50 nanometer overlying the p-type (Al,In,Ga)N waveguidingmaterial.
 10. The method of claim 1 further comprising introducing ametallorganic or a combination of metallogranic precursors consisting ofa group including trimethylgallium, triethylgallium, trimethylaluminum,trimethylindium, or Bis(cyclopentadienyl)magnesium while forming thep-type (Al,In,Ga)N waveguiding material; and wherein the p-type(Al,In,Ga)N waveguiding material is grown using MOCVD or MBE.
 11. Themethod of claim 1 wherein the substrate member is configured on anonpolar (10-10), (11-20), or a related miscut orientation.
 12. Themethod of claim 1 wherein the substrate member is configured on polar(0001) or (000-1), or a related miscut orientation.
 13. The method ofclaim 1 wherein the substrate member is configured on a semipolar(20-21), (20-2-1), (30-31), (30-3-1), (11-22), or a related miscutorientation.
 14. The method of claim 1 wherein the substrate membercomprises a misfit dislocation blocking feature.
 15. The method of claim1 further comprising forming a conductive oxide material comprisingeither an indium tin oxide material or a zinc oxide material overlyingthe p-type (Al,In,Ga)N waveguiding material; and forming a metallizationlayer selected from at least one of Au, Ni, Pd, Al, Pt, or Ti overlyingthe conductive oxide material.
 16. The method of claim 1 wherein a diodevoltage of the light emitting device is less than 6.75 V at a currentdensity of 14 kA/cm².
 17. The method of claim 1 wherein an area on thesubstrate member affected by dark spot defects is less than 10%.
 18. Themethod of claim 1 wherein a slab optical loss of the light emittingdevice is less than 10 cm⁻¹.
 19. A method for fabricating a lightemitting device configured as a Group III-nitride based laser device,the method comprising: providing a substrate member comprising a galliumand nitrogen containing material and a surface region; forming a galliumcontaining epitaxial material overlying the surface region; forming ap-type (Al,In,Ga)N waveguiding material overlying the gallium containingepitaxial material under a predetermined process condition; maintainingthe predetermined process condition such that an environment surroundinga growth of the p-type (Al,In,Ga)N waveguiding material is substantiallymolecular N₂ rich gas environment; and maintaining a temperature rangingfrom 725 C to 925 C during the formation of the p-type (Al,In,Ga)Nwaveguiding material; whereupon the predetermined process condition issubstantially free from molecular H₂ gas, the p-type (Al,In,Ga)Nwaveguiding material is formed using a trimethylgallium metallorganicprecursor and/or a triethylgallium metallorganic precursor with a growthrate greater than 0.75 angstroms per second and less than 5.0 angstromsper second; wherein the p-type (Al,In,Ga)N waveguiding material isformed at the predetermined process condition including an ammoniacontaining species, whereupon a ratio of the ammonia containing speciesto the substantially molecular N₂ rich gas is greater than 1:5 but lessthan 2:3; and further comprising forming an n-type gallium nitridematerial below the p-type (Al,In,Ga)N waveguiding material, the p-type(Al,In,Ga)N waveguiding material configured as a cladding region.
 20. Amethod for fabricating a light emitting device configured as a GroupIII-nitride based laser device, the method comprising: providing asubstrate member comprising a gallium and nitrogen containing materialand a surface region; forming a gallium containing epitaxial materialoverlying the surface region; forming a p-type (Al,In,Ga)N waveguidingmaterial overlying the gallium containing epitaxial material under apredetermined process condition; maintaining the predetermined processcondition such that an environment surrounding a growth of the p-type(Al,In,Ga)N waveguiding material is substantially molecular N₂ rich gasenvironment; and maintaining a temperature ranging from 725 C to 925 Cduring the formation of the p-type (Al,In,Ga)N waveguiding material;whereupon the predetermined process condition is substantially free frommolecular H₂ gas, the p-type (Al,In,Ga)N waveguiding material has athickness from 400 to 1000 nanometer with Mg doping level of 5E17 to2E19 atoms per cubic centimeter, the p-type (Al,In,Ga)N waveguidingmaterial being configured as a waveguiding material and a claddingregion.
 21. A method for fabricating a light emitting device configuredas a Group III-nitride based laser device, the method comprising:providing a substrate member comprising a gallium and nitrogencontaining material and a surface region; forming a gallium containingepitaxial material overlying the surface region; forming a first p-type(Al,In,Ga)N waveguiding material overlying the gallium containingepitaxial material under a first predetermined process condition;maintaining the first predetermined process condition such that anenvironment surrounding a growth of the first p-type (Al,In,Ga)Nwaveguiding material is substantially molecular N₂ rich gas environment;maintaining a temperature ranging from 725 C to 925 C during theformation of the first p-type (Al,In,Ga)N waveguiding material; andforming a second p-type (Al,In,Ga)N waveguiding material overlying thegallium containing epitaxial material under a second predeterminedprocess condition; wherein the first predetermined process condition issubstantially free from molecular H₂ gas; wherein the secondpredetermined process condition comprises a non-substantially molecularN₂ rich gas environment.
 22. A method for fabricating a light emittingdevice configured as a Group III-nitride based laser device, the methodcomprising: providing a substrate member comprising a gallium andnitrogen containing material and a surface region; forming a galliumcontaining epitaxial material overlying the surface region; forming ap-type (Al,In,Ga)N waveguiding material overlying the gallium containingepitaxial material under a predetermined process condition, thepredetermined process condition being substantially free from molecularH₂ gas; maintaining the predetermined process condition such that anenvironment during a growth of the p-type (Al,In,Ga)N waveguidingmaterial is substantially molecular N₂ rich gas environment, whilemaintaining a temperature ranging from 725 C to 925 C during theformation of the p-type (Al,In,Ga)N waveguiding material; and furthercomprising forming an n-type gallium nitride material below the p-type(Al,In,Ga)N waveguiding material, the p-type (Al,In,Ga)N waveguidingmaterial configured as a cladding region; forming an active regionoverlying the gallium containing epitaxial material, the active regioncomprising of a plurality of quantum-well regions, each of thequantum-well regions being configured with a barrier material; forming ap-type (Al,In,Ga)N p-type electron blocking layer overlying the activeregion; wherein the p-type (Al,In,Ga)N waveguiding material is grownunder the predetermined process condition consisting of thesubstantially molecular N₂ rich gas environment and a molecular H₂ to N₂gas flow ratio of less than 1 to 10; wherein the p-type (Al,In,Ga)Nwaveguiding material is grown within the temperature range during thepredetermined process condition; wherein the p-type (Al,In,Ga)Nwaveguiding material is characterized by a carbon impurity concentrationof less than 1E17 atoms per cubic centimeter when grown within thetemperature range; and wherein the p-type (Al,In,Ga)N waveguidingmaterial is formed using a trimethylgallium metallorganic precursorand/or a triethylgallium metallorganic precursor with a growth rategreater than 0.75 angstroms per second and less than 5.0 angstroms persecond; wherein the p-type (Al,In,Ga)N waveguiding material is formed atthe predetermined process condition including an ammonia containingspecies, whereupon the ammonia containing species to molecular N₂ gasratio is greater than 1:5 but less than 2:3; and wherein the substrateis configured on a nonpolar (10-10), (11-20), or a related miscutorientation or wherein the substrate is configured on polar (0001) or(000-1), or a related miscut orientation or wherein the substrate isconfigured on a semipolar (20-21), (20-2-1), (30-31), (30-3-1), (11-22),or a related miscut orientation.